


The Rules of Surviving the Multiverse

by estelraca



Category: Kamen Rider Decade
Genre: Multi, Polyamory Negotiations, Post-Decade, Post-Zi-O
Language: English
Status: Completed
Published: 2020-10-24
Updated: 2020-10-24
Packaged: 2021-03-08 18:08:58
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,657
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27180904
Author URL: https://archiveofourown.org/users/estelraca/pseuds/estelraca
Summary: Katiou and Tsukasa do come back from the world of Zi-O, which means the discussion that they have with the others when they return is much more friendly than it would have been if Natsumi and Yuusuke had to come riding in to save them.  (Nobody talks about the possibility of one of them not coming back.  That's one of the rules.)
Relationships: Hikari Natsumi/Kadoya Tsukasa/Kaitou Daiki/Onodera Yuusuke
Comments: 2
Kudos: 16
Collections: Trick or Treat Exchange 2020





	The Rules of Surviving the Multiverse

**Author's Note:**

  * For [Jen425](https://archiveofourown.org/users/Jen425/gifts).



> Thank you so much for giving me an opportunity to write this delicious group! I hope that you enjoy this little Halloween treat.

_The Rules of Surviving the Multiverse_

“You died.” Natsumi doesn't try to soften the words—the _accusation_.

Tsukasa looks up into her eyes, his posture loose and easy despite the fact that his hands are tied behind his back, keeping him sitting in the chair.

(They're not tight bonds. They're nothing that Tsukasa couldn't escape from, and Kaitou's are even looser where he's tied to another chair, back to back with Tsukasa. Natsumi and Yuusuke know better than to try to cage either of them, but especially Kaitou. These two stay because they want to; the moment they feel they don't have a choice is the moment they'll be gone. Later, after they've worked out this latest mess, after they've had a chance to be comfortable with each other again, _then_ the bonds might be tight. Then there might be time for something rougher, fiercer. But not yet. Not right now.)

“I didn't _die_ , I just...” Tsukasa trails off, one long leg stretching out to try to hook between Natsumi's.

Kaitou cranes his head over his shoulder to try to see Tsukasa. “He one hundred percent died. If not for me he would not be breathing.”

“You think way too highly of yourself, Kaitou.” Tsukasa rolls his head back on his neck, glaring at the ceiling in lieu of Kaitou.

Natsumi dodges Tsukasa's leg, moving forward, straddling his lap and staring down at his face. One hand buries itself in his hair; the other cups his chin. “What's the rule about dying?”

“Don't die.” Tsukasa's tone is suddenly all utter seriousness as he stares up into her eyes.

Natsumi shakes her head.

Tsukasa draws in a breath and lets it out in a huff. “Don't die alone. If you think something's serious enough death might happen, make sure to bring others. I _did_. I brought Kaitou.”

“Who _also_ tried to die.” Yuusuke shoves himself off the counter, stalking towards Kaitou.

Kaitou actually turns his attention away from Tsukasa, watching Yuusuke approach with an expression that is hungry and wanting and wary all at once. “I was less dead than Tsukasa.”

“But more possessed, right?” Yuusuke buries his hand in Kaitou's hair, holding tight as he leans Kaitou's head back. “What's the rule about possession, Kaitou?”

“There can't be rules about possession, because—”

Yuusuke leans down to bite the tip of Kaitou's nose, then to trail a series of nips up Kaitou's neck.

Kaitou gives a little yip, one that could be pleasure or pain, and scowls at Yuusuke. “If there's a danger of possession, bring in everyone. No one is to be possessed when there aren't others there to free them. I did have Tsukasa there. It's not my fault he's useless.”

“Useless? Who's the one who—” Tsukasa's voice is cut off mid-protest, and Yuusuke is fairly certain Natsumi is kissing him.

Yuusuke can't actually _see_ Tsukasa and Natsumi, his gaze too busy holding Kaitou's stare. He will be able to out-stare Kaitou—one of the more useless gifts the amadam gives him—but Kaitou continues to insist on trying to best him. “Being possessed isn't something to joke about, Kaitou.”

“Sometimes it is.” Kaitou grins, though his eyes still have that wariness to them, that willingness to either fight or run that defines Kaitou's life even a decade after the worst of their pains. “Sometimes it's hilarious and results in you—”

Yuusuke decides to take a card out of Natsumi's playbook and leans down to kiss Kaitou firmly on the mouth. It does get Kaitou to stop talking, his lips immediately melding to Yuusuke with a familiarity and hunger that makes warmth of a different sort from the amadam's course through Yuusuke's guts.

Natsumi's hand on his shoulder causes Yuusuke to break the kiss, and he lets go of Kaitou's hair, taking a step back. The kissing and the hugging and the _more_ will come later, after they've finished their conversation. But sometimes the best way to get Tsukasa and Kaitou to actually participate in a conversation is to set it up like this, to make it the prelude to more desired promises, and both Yuusuke and Natsumi have gotten very good at playing the game over the years.

“Come on, Natsumi.” Tsukasa is rolling around in his chair in a way that shouldn't be possible with a human spine, trying to see them. “I didn't know what I was walking into at first, but then I _had_ to stay. The disturbance I found... he wasn't like me, but he was.”

Yuusuke frowns, looking at Natsumi.

Natsumi shrugs, going back over to face Tsukasa. “Is this why you rushed in here, grabbed the K-touch, said 'universe is haunted', and ran back out?”

Kaitou bursts out laughing. “That's _my_ type of line. You're not allowed to steal from me, Tsukasa.”

“I didn't steal from you, I just wanted to get back to what I was doing.” Tsukasa's tone is sulky as he tosses his head back, clearly trying and failing to hit Kaitou. “There was a boy. His name's Tokiwa Sougo. He had a gift, and because of that this man manipulated his life, tried to make him into a king and a monster.”

Yuusuke glances to Kaitou, but Kaitou's face is blank, his eyes fixed downward. Whatever happened in the world of Zi-O, it shook the both of them.

“Kaitou?” Yuusuke presses his hand to Kaitou's cheek.

“He wasn't like Tsukasa.” Kaitou looks up at him. “Sougo. He wasn't anything like Tsukasa, but that was just because they hadn't been able to take away his _caring_. They made him want to be king, but he wanted to be a _good_ king. He wanted it so badly, and they wanted to break him for it. They wanted to break all the universes for their own power, their own greed.”

Yuusuke bends down, his other hand cupping Kaitou's face, looking into the thief's eyes.

“I steal what I want.” Kaitou's voice is a fierce, raspy whisper. “And I wanted the four of them safe.”

“Four...?” Natsumi's voice is also rough, and Yuusuke doesn't need to look to see that she's also starting to understand why Tsukasa and Kaitou broke the rules.

“They aren't us.” Tsukasa tries to sound nonchalant, but Yuusuke knows every nuance of his voice, every tic and twitch of his shoulders. “There's no one in their group as stupidly good as Yuusuke, or as ridiculously petty as Kaitou, or as absolutely perfect as you.”

Natsumi's eyebrow twitches up, a suppressed smile, but she just crosses her arms and waits for Tsukasa to continue.

Tsukasa sighs. “There were four of them. Two time travelers and a prophet and a boy who wanted to be king so he could save the world. And I had a chance to help them. So I took it.”

Yuusuke reaches over Kaitou's shoulder to give Tsukasa's head a little shove. “All you had to do was _tell us_ how dangerous it was. Natsumi and I could have helped.”

“You were a little busy.” Kaitou bites at Yuusuke's sleeve, a little nip that does nothing more than dent the fabric. “And it's not like _you_ always come and tell _us_ when things are bad, either. That world you found where the Ultimate Darkness had enveloped everything... how long did it take you to admit to us what it was?”

Yuusuke shivers at the unexpected blow. From Kaitou, though, it really shouldn't be so unexpected. When Kaitou's feeling guilty, he lashes out; when Kaitou's feeling trapped, he hits below the belt as hard as he can. Sometimes it's like loving a feral cat, and just like with a feral cat, he's at his most dangerous when he's been through something difficult. “That was different. I wasn't diving in there to see what I could find without the rest of you. I was just... trying to decide if I could even handle searching.”

He had, in the end. He'd gathered the others and they'd devised a plan and Yuusuke had found his broken brother and offered a peaceful end. But it hadn't been simple and it hadn't been painless and it has nothing to do with what Kaitou and Tsukasa did.

Yuusuke narrows his eyes, drawing a breath before letting it out in a sigh. Giving his head a shake, he settles himself on Kaitou's lap, earning a startled squeak from Kaitou. Resting his forehead against Kaitou's, Yuusuke drapes his arms around Kaitou's shoulders. “Is it really so hard to say that you're sorry for worrying us?”

“I don't say sorry.” Kaitou shifts his head, his lips brushing against Yuusuke's nose in a kiss. “You know that.”

“You could start.” Yuusuke digs his fingers into Kaitou's back—carefully, not with nearly the force he could, keeping the amadam's strength in check. “You could just say 'Yuusuke, Natsumi, I didn't mean to get possessed or almost die or almost destroy the multiverse without you'. I can walk you through it word by word.”

“You'd need to, because he's not—” Tsukasa's voice is once again cut off by Natsumi's kiss.

“Yuusuke...” Kaitou's breath is warm against him, and Yuusuke presses their lips together, enjoying the feel of Kaitou's skin against his.

One of Kaitou's hands is abruptly free, burying itself in Yuusuke's hair.

Yuusuke pulls back, glaring at Kaitou.

Kaitou shrugs. “You didn't really think these ropes would hold me, did you?”

No, no he didn't, but Kaitou's cheating to point it out. Kaitou's breaking the game, and he hasn't shown any understanding of what he did, of how much it—

Kaitou's hand cups Yuusuke's cheek. “I'm sorry.” He turns to Natsumi. “I'm sorry I broke the rules. I won't do it again. Not unless _this_ one—” He gives the back of his chair and thus Tsukasa's chair a shove. “Makes it necessary.”

“This was not my fault.” Tsukasa tugs on his ropes, giving Natsumi a wounded look. “It really wasn't.”

“It doesn't matter whose fault it was.” Natsumi bends over Tsukasa, pressing herself against him as she pulls the right rope to release the knots. “This isn't about fault, it's about making sure we're all still here. It's about seeing the multiverse and helping where we can and also...” Natsumi's voice catches, and she places a hand on Tsukasa's chest. “And also making sure we all make it home.”

“We did.” Tsukasa kisses her, firm and certain, before turning to face Yuusuke and Kaitou. “We all did, and we all will.”

“We'll try.” The words are a whisper from Kaitou into Yuusuke's ear, a promise as rare and precious as an apology.

There aren't many words for the hour that follows. There don't need to be many. They know each others' bodies after all these years. They know what each likes, what each wants, what will hurt and what will help and what doesn't matter.

When they're done, there's dinner with Eijiro. As usual the old ex-villain seems either unaware or unconcerned with the exact dynamics of the family that has formed in his house. He's just glad to have them all home, and tells them so with words and cookies.

They sleep in the same room, on a collection of futons all shoved together. They don't, always. Sometimes it's nice to have a room to oneself, or to have a night with just one other person to focus on. But tonight, after they've been apart—after there's been danger... for tonight, it's better to be together.

“New rule.” Natsumi's voice is sleep-slurred, but Yuusuke can tell from the various sounds of curiosity that arise that everyone is still awake.

Tsukasa's lips nuzzle behind Yuusuke's ear. “We have too many rules already. Yuusuke won't be able to remember them all if we keep adding more.”

Yuusuke elbows Tsukasa.

Natsumi drapes her body across the both of them, kissing Yuusuke on the mouth before turning to Tsukasa and putting a hand over his. “New rule. If we meet anyone that reminds us of a younger Tsukasa, we kidnap him.”

That was not what Yuusuke was expecting, and he has to process the words for a moment, making sure he heard them right.

Kaitou laughs. “What, just bring him back here?”

Natsumi nods. “Him and any of his friends that you need to.”

Yuusuke starts to sit up. “Natsumi, we can't just kidnap people from other worlds—”

His objection is interrupted by Kaitou kissing him and placing a _very_ suggestive hand that causes Yuusuke's whole body to arch.

Natsumi curls her body so that she's lying more solidly atop Yuusuke, which doesn't help with Kaitou's teasing. “We can. Just briefly. If they come willingly, all the better. But if we insist that anyone like Tsukasa is brought here, that means no one gets to make stupid decisions without consulting the rest of us.”

“I'm pretty sure that's both not true, given us, and that it's a terrible lesson to take away from— _oh_.” Yuusuke loses his train of thought briefly as Tsukasa presses one hand gently, achingly, _wonderfully_ over the amadam, and Natsumi's hands are on his chest, her hips straddling his, and he would complain except it's not the first time they've used physical closeness to handle difficult conversations. Yuusuke shivers. “This isn't going to make me forget we're planning kidnappings.”

Kaitou gives a dramatic sigh. “You really think far too much.”

“No.” Tsukasa leans in to kiss Yuusuke's mouth. “He _feels_ far too much.”

That _is_ true, his nerves all on fire, but it's a sensation he's come to love and cherish over the years. “Having morals isn't a failing.”

“We _want_ you to have morals.” Tsukasa kisses him again, deep and long. “If you didn't, then the rest of us would be in even more trouble.”

“I'm suggesting kidnapping.” Natsumi lays her body against his, and Kaitou must have been busy taking off her shirt while Tsukasa kissed Yuusuke, because it's her bare skin against his when she settles against him. “But I'm doing it for a good reason. If we kidnap them, it ensures that we all get a chance to meet them, _and_ it gives the person a chance to think. Because getting a chance to think, to be proactive rather than reactive... that's something I think far too few young Riders or heroes in general get. It's altruistic kidnapping, really.”

Yuusuke can't help a laugh. “You've been spending too much time with Kaitou.”

“Probably true.” Natsumi's mouth is gentler than Tsukasa's, more inviting, less demanding. “But that's just because I want to be annoyed by him for a long, long time.”

Yuusuke smiles, ignoring Kaitou's rejoinders. “All right. If we meet anyone like Tsukasa, we immediately try to bring him here. I'm all right with that being a new rule.”

They don't have many rules for traveling the multiverse. _Don't go into a deadly situation alone._ That's been an important one for all of them, though because of different factors.

_Don't go into a situation involving possession without_ everyone _being aware._ That one they had decided after one too many painful situations, and it has served them well.

_Don't assume you know a world just because it looks familiar._ That one, too, they had learned through painful experience.

And now _kidnap anyone who reminds us too much of our younger selves_. Which is, really, just another way of saying _don't let the mistakes of the past repeat_. That's what their whole journey has been about, hasn't it? Fighting free of the past. Creating a better present. Holding on to that present with all their might, despite anyone who might try to take it from them.

With his lovers all around him and a long, beautiful night ahead, Yuusuke decides that it all boils down to one rule, really.

_Come home_.

No matter what, they all need to come home.

So long as that happens, they can hammer the rest into place. Love can make for some fantastically tough nails, after all.


End file.
